Production of a light-fast azoic pigment



Patented Aug. 8, 1950 a corporation of Maine PRODUCTION OF A LIGHT-FAST AZOIC I o t PIGMENT Maurice G. Powell, Bound Brook, N. .32, assignor to American 'Cyanamid Company, New York, N. Y.,

No Drawing. Application November 10, 1947, I

Serial No. 785,191

4 5 Claims, lot 2 6 -181 'fes'tness'is' enormously increased. The pigment has the formula:

an x ray diffraction spectrum characterized by the following bands:

Inter-planer at Cent Spacing L. Intensity This form shouldnot be confused with the crysi tailmeirermebramea by hot acid coupling in the- ,absence of a cationic surface active agent, the X-jray diffraction spectrum of which is char acterized by a line of maifimum intensity at an heating a light unstable form of the pigment for a considerable period at a temperature above 100 C. When a light unstable pigment obtained from cold acid coupling in the absenceof a cationic surface activeagent is heat treated by the present invention, products which are identical with the other hand, when the amorphous product which results from coupling in alkaline medium is heat treated sometimes only a portion of the pigment appears to be transformed into the light fastcrystalline form described above which is characterized by an X-ray diffraction spectrum having its line ofv maximum intensity at 13.3 A. at interplanar spacings with the second most intense line at an interplanarspacing at 3.34

The temperature is not critical and mayv'ary widely. For example, a temperature as 10w as 105 C. gives good results, but temperatures below 100 C. are not satisfactory. The top limit on temperature is set bythe stability of the products to high temperatures and by me'chanical con siderations. Satisfactory results havebeen ob tained at as high a'temperature. as 200 C.

The time of heating is also not critical but should be long enough to effect the change in physical form of the pigment which appears to accompany its increased light fast'ness. transformation to the light fast crystalline form described above is ,not instantaneous but requires a considerable period of heating. .For small batches heating times of the order of several hours are satisfactory. Larger batches in some intrpianar crystal spacing of 9.2 A., and a line of next greatest intensity at an interplanar spaccases may require longer heating. In each case the. skilled chemist will determine the minimum heating time for a particular batch siz'eby. tests on-the product Once determined the timecycle does not change, so long as thebatch size and temperature are the same.

Various methods of heating at temperatures above 1009C. may be employed. One good way is to heat inlan autoclave and this is preferred.

- It is, however, also possible to heat at atmos;

pigment described above maybe prepaied by pheric pressure, inhan aqueous medium to which sufiicient soluble salt, such as calcium chloride, has been added to raise the boiling point above When autoclaving is used it is desirable to chloride to raise the boiling point above 105 C. have the autoclave surface of a material which The slurry is then heated at this temperature for does not react with the slurry. Nickel or glass Several 8 until the p m ShOWS e X- ay lined autoclaves are satisfactory, but Ordinary diffrac s ru Q'l Qrystamne iron or steel autoclaves are not desirable as convpigment is thenlfilter'ed washed and siderable decomposition results from the reaction i m the customary manner and shows a of the iron with the pigment slurry light fastness of 125 hours on the Fadeometer.

I claim: The invention will be described in more detail I 1. A method of increasing the light fastness of in conjunction with the spfecific 1 an azoic pigment from tetrazotized dianisidine amples, Whlch represent typlcail embodlments of and the orthophenetidide of 2,3-hydroxy naphthe inv n i n Th parts are by w i 1 thoic acid having the formula:

00-011; com OCH: 0H 06 HsCaO I CaHl Example 1 which comprises'heating the pigment in anaqueous medium to a temperature above 100 C.

atcho m t r ed s follows: b f the mg en 15 p epar a and below the decomposition temperature of the 6.55, parts of dianisidine are gradually wet with 7oolparts of water using adequate mechanical pigment until the pigment has been transformed agitation. 17.8 parts of 38% aqueous hydrom physical form having greatly n d chloric acid are added and the mixture stirred 3 f-aistness and e e e -"e by n y until the dianisidine is completely dissolved. The .Fhffmctlon p i g lmes of greatet a temperature is then lowered to 0 C. by the addi-" net,greatest.1ntens1tYa? mterplanar' Spacmgs of tion of ice and a 10% solution containing 7.8- M and respectlvely-I parts sodium nitriteis rapidly added with vigor- A method of increasing the light f s' s 0f ous stirring. The stirring is continued with rapid n @1010 pigment m tetra otized dianisidine agitation at 0 0. until tetrazotization is oomd t orthophenetidide of 2,3-hydro n p plete. thoic acid having the formula:

H NH v v. /NH

oo on .0011; 0cm v ion 00 H5020 I v V I i' i OCzHt ,uspsasflof orthophenetidide of 2,3-hydroxy hich comprises heatin a o s" s y o naphthoic acid are wetted with 50 parts of water the P t to a t p u between 53- 0 (1- oontaining about 1% of a wetting agent. The at superatmospheric pressure until the pigment wetting is continued until a paste is formed, hasbeen transformed intoaphysical form having whereupon another 50 parts ofwater are slowly a greatly enhanced light fastness and character-v added. The temperature is adjusted to 155 C. d by an y ract on patter vin lines andjaa arts of sodium hydroxide in the form f f r st nd n xt rea intensi y at in rof a 20% solution are added. .The product displanar spacings of and respectivelysolyes in the form of its sodium salt and 10 parts 3. A method according to claim 1 in which of sodium acetate arethen added and the volume salts are dissolved in the aqueous slurry to raise adjusted to 600 parts. Thereupon the temperaits boiling point above 100 C. and heating is efture is brought down to 0 C. with ice and 10 fected at atmospheric pressure. parts of glacial acetic acid added with vigorous 4. A method according to claim 1 in which the stirring, As soon as the coupling component has azoic pigment is obtained by coupling tetrazotized completely precipitated stirring is stopped. V 55 o-dianisidine and the orthophenetidide of 2,3-

Immediately after precipitation the coupling hydroxy naphthoic acid iii ium, the component is added to the tetrazotized dianisipressure vessel having a noncorroding, nonferdine solutionand stirred at 0 C. for several rous surface exposed to the aqueous slurry. hours Thereupon the reaction mixture is slowly 5. A method according to claim 2 in which the heated up to 90 C., which temperature is mainazoic pigment is obtained by coupling tetrazotized tained until coupling is complete. o-dianisidine and the orthophenetidide of 2,3- The slurry is then placed in an autoclave which hydroxy naphthoic acid in acid medium, the is preferably lined with nickel or glass and heated pressure vessel having a noncorroding, nonferto200 C. for several hours until the product rous surface exposed to the aqueous slurry.. shows the typical X-ray diffraction spectrum of MAURICE G, POWELL. I the light fast crystalline form with lines of greatest and next greatest intensity at 13.3 and REFERENCES CITED.

7 mterplanar. respectwely' The following references are of record in the autoclaved product shows a light fastness of 125 me of this patent; hours on the Fadeometer as compared to 40 hours forvthe product before autoclaving. UNITED STATES PATENTS Number Name I Date' Emmple 2 2,261,626 Lang Nov. 4, 1941 To a slurry of the pigment preparedas de- 94 30 i g 25, 942

scribed in Example 1 is added sufiicient calcium 

1. A METHOD OF INCREASING THE LIGHT FASTNESS OF AN AZOIC PIGMENT FROM TETRAZOTIZED DIANISIDINE AND THE ORTHOPHENETIDIDE OF 2,3-HYDROXY NAPHTHOIC ACID HAVING THE FORMULA: 